Open mail relay
From open-encyclopedia.com - the free encyclopedia.
An open mail relay is an SMTP (email) server configured in such a way that it allows anyone on the Internet to relay (i.e. route) email through it.
Until the 1990s this was the normal configuration for a mail server and was often the default on Unix systems at installation. This was due, in part, to the fact that in the early days of the internet there were not very many systems connected. It was more economic for email to be passed from computer to computer until it reached its destination than to connect directly to the target computer. Furthermore, the small number of servers on the internet applied high standards on conduct, and due to the government and educational nature of most of those servers, the transfer of commercial messages was de facto forbidden.
Nowadays, backbone networks and Internet switches make it much more reasonable to send mail directly to the target host, without need for relaying through a "middleman" site.
In the mid-1990s, once the internet became more of a public (and moreover, commercial) service, it wasn't long until it was abused by spammers. As spam soon became widely unpopular, spammers discovered that they could minimize or avoid detection by re-routing their email through third party email servers. After this practice became widespread, the mere practice of operating an open relay email server became frowned upon among most members of the Internet community. The Can Spam Act of 2003 outlaws this use in the United States.
Many ISPs use DNSBLs to prevent open mail relay servers to send mail to them. Once a mail server is detected or reported that allows third parties to send mail through them, they will be added to one or more such lists, and other email servers using those lists will reject any mail coming from those sites. This can result in legitimate mail being blocked until the problem mail server is reconfigured to prevent open relaying.
Initially, the measures taken against open mail relays caused headaches for some ISPs. To allow customers to use their email addresses at Internet locations other than the company's systems (such as at school or work), many ISPs explicitly allowed open relaying so that customers could read and send email via the ISP from any location. Such ISPs were eventually blacklisted for operating an open relay. This trend gave way to the technique of "POP before SMTP", in which an ISP subscriber at a remote location must check their email (requiring authentication) before they can send mail. This creates a temporary email relaying window for the remote network.
The most famous open mail relay is probably that of John Gilmore, who argues that running an open relay is a free speech issue, and that since he has never sent any spam personally he has a right to configure his computer however he pleases.
External links
pl:open relay
